MAX1745EUB+T Maxim Integrated Products, MAX1745EUB+T Datasheet - Page 9

• Manufacturer Part Number: MAX1745EUB+T
• Description: IC DC-DC CNTRLR STP DWN 10UMAX
• Manufacturer: Maxim Integrated Products
• Type: Step-Down (Buck)r

Specifications of MAX1745EUB+T

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.25 ~ 18 V
• Frequency - Switching: 330kHz
• Voltage - Input: 4.5 ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Power - Output: 444mW
• Output Voltage: 1.25 V to 18 V
• Output Current: 10 A
• Input Voltage: 4.5 V to 36 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

lower frequencies, reducing the MOSFET gate drive
and switching losses. In discontinuous mode, under
most circumstances, the on-time will be the fixed mini-
mum on-time of 1μs. If the inductor value is small, or
the current-sense resistor large, the current limit will be
tripped before the minimum on-time, terminating the
on-time and thus setting the fixed on-time.
If the inductance is too large, or the output capacitance
high and equivalent series resistance (ESR) low, then
the MOSFET remains on longer than the minimum on-
time, until the output capacitor charges beyond the
error comparator’s (V
causing the part to operate in hysteretic mode.
Operating in hysteretic mode results in lower frequency
operation. The transition to hysteretic mode occurs at
the critical output capacitor ESR:
Figure 2. Simplified Functional Diagram
ESR
CRITICAL
= (V
_______________________________________________________________________________________
- - - MAX1744 ONLY
OUT
OUT
( ) MAX1745 ONLY
SHDN
/ 1.25V)
/ 1.25V)
VL
✕
✕
Q
REGULATOR
REGULATOR
Q
8mV / I
LINEAR
LINEAR
MINIMUM
ONE SHOT
8mV hysteresis,
High-Voltage, Step-Down DC-DC
MINIMUM
ON-TIME
OFF-TIME
ONE SHOT
VH
VH
VL
EXT
TRIG
TRIG
RIPPLE
IN
S
Q
R
ERROR
COMPARATOR
REFERENCE
1.25
where I
determined by:
where t
mum on-time-control, or:
where t
mum off-time-control.
SHDN
REF
Controllers in µMAX
RIPPLE
OFF(MIN)
ON(MIN)
I
RIPPLE
I
RIPPLE
is the inductor ripple current, and can be
100mV
is the minimum on-time (1μs) for mini-
is the minimum off-time (2μs) for mini-
-
= (V
+
= (V
IN
OUT
- V
3/5
CS
OUT
(FB)
OUT
)
✕
)
t
OFF(MIN)
✕
t
ON(MIN)
/ L
/ L
9